In recent years, power storage systems to be applied for small apparatuses that need high energy density, such as information technology-related apparatuses or communication apparatuses, specifically, personal computers, video cameras, digital still cameras, and cell phones, and power storage systems to be applied for large apparatuses that need power, such as electric vehicles, hybrid vehicles, auxiliary power for fuel cell vehicles, and energy storage have received attention. As a candidate therefor, non-aqueous electrolyte batteries such as a lithium ion battery, a lithium battery, a lithium ion capacitor, or a sodium ion battery, have been actively developed.
Many of these non-aqueous electrolyte batteries have already been put into practical use, but none of these batteries has satisfactory properties for use in various applications. In particular, a non-aqueous electrolyte battery to be mounted on a vehicle such as an electric vehicle is required to have a high input output characteristic even in a cold season. Hence, improvement in a low-temperature characteristic is important. In addition to the low-temperature characteristic, such a battery is required to have a high-temperature cycle characteristic such that reduction in capacity is small even when charging and discharging are performed repeatedly under a high temperature environment (a high-temperature cycle characteristic) and self-discharging is small even when the battery is placed in a fully charged state for a long period of time under a high temperature environment (a high-temperature storage characteristic).
As a means for improving the high-temperature characteristic, and the battery characteristic (a cycle characteristic) wherein charging and discharging are repeated, optimization of various battery components including active materials of positive electrodes and negative electrodes has been studied. A non-aqueous electrolyte solution-related technology is not an exception, and it has been proposed that deterioration due to decomposition of an electrolyte solution on the surface of an active positive electrode or an active negative electrode is suppressed by various additives. For example, Patent Document 1 proposes that battery characteristics are improved by the addition of a vinylene carbonate to an electrolyte solution. However, there was a problem in that battery characteristics at high temperatures are improved, but the internal resistance is significantly increased to lower the low-temperature characteristic. Addition of a silicon compound to an electrolyte solution has been also studied. Alternatively, examination has been made on addition of a silicon compound to an electrolyte solution, for example, as shown in Patent Documents 2 to 6, which propose addition of a silicon compound such as a silicone compound or a fluorosilane compound, to a non-aqueous electrolyte solution for the purpose of improving a cycle characteristic of the non-aqueous electrolyte battery and for inhibiting internal resistance elevation so as to improve a high-temperature storage characteristic and a low-temperature characteristic of the non-aqueous electrolyte battery. In addition, Patent Document 7 proposes addition of a fluorosilane compound or a difluorophosphoric acid compound in order to improve a low-temperature characteristic of the non-aqueous electrolyte battery. Furthermore, examination has been conducted on the addition of a salt containing a phosphoryl group or a sulfonyl group to an electrolyte solution. For example, there have been proposed a method (Patent Document 8) for improving a high-temperature cycle characteristic or a high-temperature storage characteristic by combining a specific sulfonimide salt or phosphoryl imide salt with an oxalato complex; and a method (Patent Document 9) for improving a cycle characteristic or an output characteristic by combining a specific fluorophosphate with a sulfonimide salt.